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North Korea's bizarre regime is a ripe target for parody, whether in Chinese media or on American TV. But its test Tuesday of a nuclear weapon, following a successful satellite launch in December, is no joke.

Together, the actions give credibility — though not immediacy — to the North Koreans' plans to mount a nuclear threat to the United States. This is their third and most sophisticated test, leading to a warhead small enough to fit atop a planned long-range missile, and no one has a promising idea for stopping them.

President Obama pledged a "swift and credible" response Tuesday, as did the U.N. Security Council with North Korea's patron, China, notably joining in. But the deeper truth could be heard in the words of Susan Rice, the U.S. ambassador to the United Nations: "We'll do the usual drill."

The leading edge of the usual drill is to tighten sanctions, but they are already stringent.

Another tactic is negotiations, but North Korea has repeatedly turned them into a game of Rope-a-Dope. The U.S. and others deliver aid and ease sanctions, then the regime reneges on its promises. Obama has wisely sworn off that strategy.

A newer suggestion — and a bad one — is to simply recognize North Korea as a nuclear power. That would have repercussions in Iran and would offer no deterrence.

The extreme choice is to attack North Korea's nuclear and missile sites. The Clinton administration came within a hair of doing just that. But the potential consequences, including a new Korean war, are both severe and unpredictable.

Obama mentioned missile defense in his State of the Union Address on Tuesday. North Korea has always seemed the nation it would work best against. But that's an incomplete solution, as are all the others.

There is, in fact, just one way to push North Korea safely off the nuclear path, and that is for China to do it. Without China's aid and patronage, the isolated and impoverished nation led by Kim Jong Un, the young third-generation dictator, would surely collapse.

The Chinese see their communist neighbor as a buffer, and they fear that strangling the Kim dynasty would send refugees streaming over the border. But to the extent that China's new leader, Xi Jinping, wants to strengthen relations with the United States, he has no better card to play than clamping down on the Kim regime. China, after all, doesn't benefit from a nuclear North Korea. It just tolerates its troublesome protégé.

That is where the focus of U.S. policy is and should remain. It may be the "usual drill," but it is the only drill available.